Welcome Guest! If you are already a member of the BMW MOA, please log in to the forum in the upper right hand corner of this page. Check "Remember Me?" if you wish to stay logged in.

We hope you enjoy the excellent technical knowledge, event information and discussions that the BMWMOA forum provides.
Why not take the time to join the club, so you can enjoy posting on
the forum, the club magazine, and all of the discounts and benefits the BMWMOA offers?Want to read the MOA monthly magazine for free? Take a 3-month test ride of the magazine; check here for details.

If this is your first visit, be sure to
check out the FAQ by clicking the
link above. You will need to join the MOA before you can post: click this register link to proceed. To start viewing messages,
select the forum that you want to visit from the selection below.

NOTE. Some content will be hidden from you. If you want to view all content, you must register for the forum if you are not a member, or if a member, you must be logged in.

I just checked out the site suggested above by Red100rt. Fascinating. It's the first time I realized that the stock BMW clutch discs don't have springs in them, circling the hub. All car discs I think I have ever replaced had those springs in them. And those auto discs were usually around $75. The discs shown on that site, developed with racing in mind, seem like the best idea. And at $375, although still unbelievably overpriced, they look like they would ease the strain on the splines considerably, and last a good long while. And they are probably still cheaper than BMW's stock discs, although I haven't checked. If mine needs replacing in the future, I think that is the route I will go, and get their spline grease also.

I strongly disagree with Chris's analysis. R bike spline failure is caused by radial misalignment between the engine crankshaft axis and the transmission axis. Adding another 20% to the spline length won't significantly change the spline life if there is radial misalignment.

that is ONE of the causes of spline failure, but misalignment is not the only cause. lack of lube from the factory, along with failure to lube on a regular basis (~ every 40-50K is advised) are the other 2 causatives.
If your splines die early and often (25-40K), that is an alignment issue. but if your splines die in the 60-90K mile range, that is a lubrication issue.
that is the reason that those who experience early spline failure also experience successive failures within a short time, as well as why some experience no or very infrequent failures. if it was only about misalignment, we would all see the same failure intervals, yet we don't.

I just checked out the site suggested above by Red100rt. Fascinating. It's the first time I realized that the stock BMW clutch discs don't have springs in them, circling the hub. All car discs I think I have ever replaced had those springs in them. And those auto discs were usually around $75. The discs shown on that site, developed with racing in mind, seem like the best idea. And at $375, although still unbelievably overpriced, they look like they would ease the strain on the splines considerably, and last a good long while. And they are probably still cheaper than BMW's stock discs, although I haven't checked. If mine needs replacing in the future, I think that is the route I will go, and get their spline grease also.

my splines died at 72K (a month before i was going to do a lube job on them). i asked about using one of the aftermarket racing clutches- stronger is better, right? was STRONGLY advised against using one, as their operation was much too grabby for street use. this was by an independent shop (so no "company prejudice" to influence his recommendation) where owner and head wrench have many decades of racing experience, and are totally willing to to utilize aftermarket parts, wehn appropriate.
no estimation on RBR's product, just sharing some general observations and alternative considerations.

I just checked out the site suggested above by Red100rt. Fascinating. It's the first time I realized that the stock BMW clutch discs don't have springs in them, circling the hub. All car discs I think I have ever replaced had those springs in them. And those auto discs were usually around $75. The discs shown on that site, developed with racing in mind, seem like the best idea. And at $375, although still unbelievably overpriced, they look like they would ease the strain on the splines considerably, and last a good long while. And they are probably still cheaper than BMW's stock discs, although I haven't checked. If mine needs replacing in the future, I think that is the route I will go, and get their spline grease also.

I'm curious about the spline engagement issue Chris has shown. The M97 gearbox combined with a clutch from 2004 in my 1995 R110RS showed nearly full spline engagement based on the wear on the clutch hub.

I do believe that low RPM riding may aggravate the issue, but the fact that he makes no mention of misalignment as a possible factor is unfortunate. When the day comes that I have to replace the input shaft on my bike, alignment and runout are the first things I'm checking.

The issue of full spline engagement is on the 6 speed transmission only.

those that have had the recurring and frequent failure issues have found that by careful measurement and relocation of one or more dowel pins (remove, fill and re-drill) that their failure issues due to misalignment were eliminated.

If it was only about misalignment, we would all see the same failure intervals, yet we don't.

While I agree that misalignment isn't the only factor, assuming that if it were only misalignment, the result would be similar failure intervals is incorrect. first off, it is safe to assume that every bike has misalignment to some degree in the crank shaft / clutch / input shaft interface. The more severe this misalignment is, the faster the splines will wear. When you work from one end of the clutch to the other, you see a whole lot of potential for misalignment:

clutch disc runout

input shaft runout

bearing runout

transmission housing bolt and dowel hole to bearing bore positioning

transmission housing bearing bore to mounting face perpendicularity

engine case bolt and dowel hole to bearing bore positioning

engine case bearing bore to mounting face perpendicularity

bearing runout

crankshaft runout

flywheel / clutch housing runout

clutch cover mounting face to clutch face parallelism

When you figure there are allowable machining tolerances for every one of these parts / assemblies which will stack together to cause varying degrees of misalignment on each motorcycle ever produced, you can expect there to be variations in spline life and lube requirements. Maybe the really short lived splines were on bikes where some of the machining was out of spec or where the spec was deviated in order to keep production going. Unless you have access to BMW's drawings and production records, you'll probably never know the full story. It is possible that the design was great, but the tolerances were never quite achievable in production. It could be that the design was compromised. At this point, it doesn't matter that much. BMW isn't going to fix it for us and it is up to each owner to decide how they want to deal with it.

There are 2 locating hollow dowel pins that align the transmission to the engine. The assembly technique has no options.

I'm speculating that the oilhead clutch housing is structurally weak and easily deformed - so much so that even if the two alignment pins are in place, spline alignment isn't assured. The clutch housing is a thin aluminum alloy die casting and has a major cutout for the starter.

The alignment problems may well be at the factory where the fixture for machining the raw casting allows things to be deformed while being machined. Next it may be a factory assembly technique where the clutch disk alignment tool isn't being properly used. Lastly it may be a field re-assembly error. Mixed in with all this is the factory's spline lube question itself.

The reason I doubt a casual machining error is that the clutch housing etc is most certainly made on a numerical machining center. These things are very accurate but only as long as the part isn't released from the fixture. It is especially suspicious that this problem has been ongoing over such a wide range of production years and would surely have caught BMW quality control attention via excessive warranty repairs.

I checked the drawing. It does look like there is a spring right inside the housing on the 5 speed M93-M94 transmissions. I assume that does the trick. That, and the comment by Bikerfish that they aren't recommended means I will be getting the stock disc, if needed. Good. I usually prefer stock components, and in this case they are in fact cheaper. Interesting that RBS is another aftermarket company/repair shop touting the fact that they know more than the BMW engineers, and that we are fools to buy the German designed stuff.

I checked the drawing. It does look like there is a spring right inside the housing on the 5 speed M93-M94 transmissions. I assume that does the trick. That, and the comment by Bikerfish that they aren't recommended means I will be getting the stock disc, if needed. Good. I usually prefer stock components, and in this case they are in fact cheaper. Interesting that RBS is another aftermarket company/repair shop touting the fact that they know more than the BMW engineers, and that we are fools to buy the German designed stuff.

Besides - there is much more torsional compliance (which is good) in the gearbox spring system than there is in the alternate clutch disk model.